* Fix broken hosted-paper link and typos in topic READMEs
The FRP index links the hosted paper as
[Deprecating the Observer Pattern](deprecating-the observer-pattern.pdf).
The file on disk really is named with a space, but an unescaped space is not
allowed in a CommonMark link destination, so the entry renders as literal text
instead of a link. Percent-encode the space so it resolves to the committed PDF.
Also correct misspellings in paper titles and descriptions:
- Algorithims -> Algorithms (comp_sci_fundamentals_and_history)
- simplifed -> simplified (data_structures)
- sucessful -> successful, numberator -> numerator,
demoninator -> denominator, authoratitative -> authoritative
(information_retrieval)
- Expresions -> Expressions (logic_and_programming)
- represention -> representation (mathematics)
- Probablistic -> Probabilistic (robotics, sublinear_algorithms)
- Philppe -> Philippe (streaming_algorithms)
* Rename the Deprecating the Observer Pattern PDF to drop the space
Per review, renaming the file rather than percent-encoding the link.
* Remove gittr and Slack links, replace with Discord
* Update Rivest paper link
* Update link for No Silver Bullet
* Update link to Event Driven FRP
* Update link to Realizing quality improvement paper
